1. Field of the Invention
This invention relates to a magnetic recording disk cartridge, and particularly to a cartridge for accommodating a very thin and small magnetic recording disk which is adapted to rotate at a high speed about its center when recording and reproducing video signals.
2. Description of the Prior Art
As is well known, a magnetic recording disk or floppy disk consists of a flexible polyester sheet disk having a magnetic substance applied to both sides of the disk sheet for recording digital information. The floppy disk has been widely used as a recording medium for computers because it is easy to handle and inexpensive to produce.
A still camera using a floppy disk in place of a photographic film has been invented. In this camera, in addition to the advantages mentioned above, the floppy disk can be used repeatedly in taking pictures. This repeated use is characteristic of a magnetic recording medium, and cannot be realized with a conventional silver halide-coated film. To be appropriate for the purpose of taking pictures, however, the floppy disk must be small in size, specifically small in diameter and thin in thickness, and the casing for accommodating such a small floppy disk for use in a still camera must be reduced in size accordingly. In this connection it has been proposed that a cased magnetic recording disk or hard floppy disk (hereinafter referred to simply as "cartridge") be rotated at a high-speed during recording and playback. This has led to the appearance of a magnetic recording type 35 mm still camera.
Reusable recording medium units are equipped with means for preventing any erroneous erasing of recorded information due to a wrong operation by the user, and generally such erroneous erasing preventing means is provided by designing the casing to enable the user to partly change its shape according to whether the required condition is "erasing forbidden" or "erasing permitted".
For instance, in case of a floppy disk or an audio-cassette, an associated casing is partly notched, or is provided with a recess in its side, and then a piece of adhesive tape or a label is applied to the notched part or recess of the casing when erasing is permitted, and the piece of tape or the label is removed when erasing is forbidden.
Applying and removing a piece of adhesive tape or a label to and from the casing is inconvenient and troublesome. Still disadvantageously, repeated use of the adhesive tape or label will cause its adhesiveness to deteriorate to the point where the tape or label will easily peel off from the casing, so that the state of "erasing forbidden" is not assured at all times. The same defect appears when the adhesiveness deteriorates with time.